Viral hemorrhagic septicemia virus (VHSV) is a viral pathogen that causes severe loss of many cultured fish including flatfish, and is regarded as a cause of viral hemorrhagic septicemia (VHS).
VHS was first reported as a critical viral disease of the rainbow trout. However, it has been recently reported that VHS occurs in various fish, including not only salmonidae fish, such as trout, rainbow trout, coho salmon, brook trout, brown trout, or steelhead trout, but also fish in natural water system, such as cod or herring, and cultured marine fish, such as flatfish, and that VHS occurs predominantly in Europe, North America, and Asia.
In South Korea, VHS has been consistently reported in Gyeongbuk and Jeju areas since it was first reported in flatfish in 2001. In particular, VHS causes mortality not only in small fish, but also large fish from late autumn to spring seasons, when the water temperature falls below 14° C. When examining the infected flatfish with the naked eyes, body color darkening, systemic bleeding, abdominal distension and hernia by abdominal reservoir, gill fading, red spot-like hemorrhage on a blind side, or the like are observed.
VHSV is a negative single-stranded RNA virus, which was first reported at the Symposium on Fish Pathology held by the World Organization for Animal Health in 1963. VHSV is bullet-shaped, approximately 180 nm in length and 60 nm in diameter, and has a size of 11 kb. VHSV belongs to the family Rhabdovirus containing six genes, nucleocapsid protein (N), polymerase-associated phosphoprotein (P), matrix protein (M), surface glycoprotein (G), a unique non-virion protein (NV), and virus polymerase (L), and among the six proteins producing the VHSV, the NV protein has been reported to be associated with the pathogenicity of the VHSV.
The VHSV is genetically mutated at a very high rate, and thus, new variant VHS viruses are constantly on the rise.
However, as a result of analyzing total gene sequence information of low pathogenic VHSV and highly pathogenic VHSV that are obtained in South Korea, there was no difference in NV gene sequences that have been reported to be related to the pathogenicity of the VHSV. In this regard, research on the early detection method of new VHSV with high pathogenic is essential for the protection of flatfish and various fishes at home and abroad.